This document introduces a new method and system for a sustainable . . . high-performance . . . low-energy consumption combination of direct and indirect evaporative cooling processes providing maximum cooling at maximum energy efficiency called the Multistage Evaporative Cooling System (MECS). The method and system of the MECS uses a water-into-ambient-air evaporation process.
Water evaporation processes for a variety of comfort and process-cooling needs have existed for many centuries. The most current representative applications of evaporative cooling are the home evaporative air coolers (swamp coolers) and commercial and industrial cooling towers. The cooling apparatuses are relatively simple in design and operation, and they evaporate water directly into ambient air from different types of wet media, which usually have large surface areas. Physics limits the temperature that these cooling apparatuses can achieve when cooling air or water. The wet bulb temperature of the ambient air and the cooling system's design primarily govern the cooling apparatus's low-temperature limit. But regardless of the design of these single stage evaporative cooling apparatuses, the wet bulb temperature of the ambient air is the theoretical absolute low limit for the achievable final temperature of the cooled media (air or water). In other words, under no circumstances can the final temperature of the cooled media for the above apparatuses achieve a value equal to or lower than the ambient air's wet bulb temperature: there will always be some difference between the wet bulb temperature of the ambient air and cold air or water from the apparatus. This temperature difference is defined as an “approach temperature”. The approach temperature value varies greatly depending on the cooling apparatus's design. The temperature of the cold air or cold water from the adiabatic cooling apparatus will always be higher than the wet bulb temperature of the entering air being cooled by the apparatus. In other words, the approach temperature of the adiabatic cooling apparatus equals the temperature of the cold water produced by the apparatus minus the wet bulb temperature of the entering air. For general applications of these cooling apparatus, the approach temperature is within a range of 5 to 10° F.
The design of invention embodiments arises from applying engineering principals to discover component arrangements and sequencing of components that result in the ambient air wet bulb temperature barrier being lowered.
Another way of stating the above is as follows. In traditional single-stage direct evaporative cooling, the evaporative cooling process lowers the dry bulb temperature of the processed air (ambient air or a mixture of ambient air and return air), while the wet bulb temperature and enthalpy of the processed air are not changed—they are equal to their initial values. In the single-stage direct evaporative cooling process, the initial wet bulb temperature of the adiabatically processed air is the absolute theoretical temperature limit for the dry bulb temperature of the adiabatically cooled processed air. As stated above, the difference between the dry bulb temperature of the adiabatically cooled air and its wet bulb temperature is known as the “approach temperature”.
This principal establishes the following: the lower the approach temperature the higher the efficiency of the adiabatic cooling process. The single stage direct evaporative cooling system/unit is not capable of achieving required temperature levels of cooling media (air or water) that is appropriate for practical use in a majority of demanding cooling applications.
Therefore, there is a strong need for the creation of new universal methods and systems allowing maximum utilization of the laws of thermodynamics related to evaporative cooling applications providing effective and energy efficient evaporative cooling systems for a wide variety of applications by using methods incorporating multiple stages of evaporative cooling.